Purpose
To restore a matrix after it has been transformed by applying balancing transformations (permutations and scalings), as determined by LAPACK Library routine DGEBAL.Specification
SUBROUTINE MB05OY( JOB, N, LOW, IGH, A, LDA, SCALE, INFO )
C .. Scalar Arguments ..
CHARACTER JOB
INTEGER IGH, INFO, LDA, LOW, N
C .. Array Arguments ..
DOUBLE PRECISION A(LDA,*), SCALE(*)
Arguments
Mode Parameters
JOB CHARACTER*1
Specifies the type of backward transformation required,
as follows:
= 'N', do nothing, return immediately;
= 'P', do backward transformation for permutation only;
= 'S', do backward transformation for scaling only;
= 'B', do backward transformations for both permutation
and scaling.
JOB must be the same as the argument JOB supplied
to DGEBAL.
Input/Output Parameters
N (input) INTEGER
The order of the matrix A. N >= 0.
LOW (input) INTEGER
IGH (input) INTEGER
The integers LOW and IGH determined by DGEBAL.
1 <= LOW <= IGH <= N, if N > 0; LOW=1 and IGH=0, if N=0.
A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
On entry, the leading N-by-N part of this array must
contain the matrix to be back-transformed.
On exit, the leading N-by-N part of this array contains
the transformed matrix.
LDA INTEGER
The leading dimension of the array A. LDA >= max(1,N).
SCALE (input) DOUBLE PRECISION array, dimension (N)
Details of the permutation and scaling factors, as
returned by DGEBAL.
Error Indicator
INFO INTEGER
= 0: successful exit;
< 0: if INFO = -i, the i-th argument had an illegal
value.
Method
Let P be a permutation matrix, and D a diagonal matrix of scaling
factors, both of order N. The routine computes
-1
A <-- P D A D P'.
where the permutation and scaling factors are encoded in the
array SCALE.
References
None.Numerical Aspects
2 The algorithm requires O(N ) operations.Further Comments
NoneExample
Program Text
NoneProgram Data
NoneProgram Results
None